global {
    objective toLeft(A, B)
    objective sameHeight(A, B)
    objective sameX(A, B) 
    constraint sameSizeAs(A, B) 
}

Set s {
    shape = Ellipse { 
      text = Auto
    }

    objective centerLabel(s, s.shape.label)
}

Map f p q {
    shape = Arrow {
        start = p
        end   = q
        text = Auto
    }

    objective centerLabel(f, f.shape.label)
}

